3分之1+4分之3+6分之5+21分之8+28分之11+42分之13
=1/3+3/4+5/6+8/21+11/28+13/42
=4/12+9/12+10/12+8/3*1/7+11/4*1/7+13/6*1/7
=23/12+1/7(32/12+33/12+26/12)
=23/12+1/7*91/12
=23/12+13/12
=36/12
=3
3分之1+4分之3+6分之5+21分之8+28分之11+42分之13
=1/3+3/4+5/6+8/21+11/28+13/42
=4/12+9/12+10/12+8/3*1/7+11/4*1/7+13/6*1/7
=23/12+1/7(32/12+33/12+26/12)
=23/12+1/7*91/12
=23/12+13/12
=36/12
=3